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In this paper, we propose a new dynamic IRS beamforming framework to boost the sum throughput of an intelligent reflecting surface (IRS) aided wireless powered communication network (WPCN). Specifically, the IRS phase-shift vectors across time and resource allocation are jointly optimized to enhance the efficiencies of both downlink wireless power transfer (DL WPT) and uplink wireless information transmission (UL WIT) between a hybrid access point (HAP) and multiple wirelessly powered devices. To this end, we first study three special cases of the dynamic IRS beamforming, namely user-adaptive IRS beamforming, UL-adaptive IRS beamforming, and static IRS beamforming, by characterizing their optimal performance relationships and proposing corresponding algorithms. Interestingly, it is rigorously proved that the latter two cases achieve the same throughput, thus helping halve the number of IRS phase shifts to be optimized and signalling overhead practically required for UL-adaptive IRS beamforming. Then, we propose a general optimization framework for dynamic IRS beamforming, which is applicable for any given number of IRS phase-shift vectors available. Despite of the non-convexity of the general problem with highly coupled optimization variables, we propose two algorithms to solve it and particularly, the low-complexity algorithm exploits the intrinsic structure of the optimal solution as well as the solutions to the cases with user-adaptive and static IRS beamforming. Simulation results validate our theoretical findings, illustrate the practical significance of IRS with dynamic beamforming for spectral and energy efficient WPCNs, and demonstrate the effectiveness of our proposed designs over various benchmark schemes. [ABSTRACT FROM AUTHOR]

This paper explores the feasibility and scope of co-channel coexistence between a low data rate Orthogonal Frequency Division Multiplexing (OFDM) secondary network and a digital television (DTV) broadcast network operating in the same area. Since DTV receivers do not transmit, neither the presence nor the impact of interference from the secondary network on these DTV receivers can be known. Consequently, conventional spectrum sensing techniques cannot be employed effectively. This paper proposes to compensate the lack of feedback by combining the available information about population distribution in the region - ranging from coarse population density estimates to accurate geospatial maps - with better estimation of interference using a data-driven technique called Ordinary Kriging. Radio Environment Maps constructed using the Kriging method from field-reported observations from the secondary nodes are used to obtain better accuracy than the conventional statistical models. The estimates are then used to compute communication parameters for each secondary link in terms of power, number of active subcarriers, and active time slots, while keeping the average interference in the DTV network within threshold bounds. Thus, the viability of such co-channel license-exempt operation of secondary networks in the DTV black and grey spaces for low data rate applications in densely populated urban areas and higher data rate capabilities for sparsely populated rural areas is established. [ABSTRACT FROM AUTHOR]

In this paper, we consider a mobile molecular communication (MC) system consisting of two mobile nanomachines, a transmitter and a receiver, propelled by a positive drift velocity and Brownian motion in a realistic blood-vessel-type flow regime. Considering the nonlinear movement of the nanomachines, an extended Kalman filter is employed to estimate the distance from the transmitter. Furthermore, based on the predicted distance, to keep the number of received molecules for bit 1 at a stable level, we employ power control on the number of transmitted molecules based on the distance between the transmitter and the receiver and the residual molecules in the channel from the previous transmission. Finally, the optimal detection threshold is obtained by minimizing the error probability. It is verified that a fixed optimal detection threshold can be effective for the power control scheme in the mobile MC. The bit error rate (BER) performance of our scheme is verified via simulation results. [ABSTRACT FROM AUTHOR]

The increasing demands of power supply and data rate for mobile devices promote the research of simultaneous wireless information and power transfer (SWIPT). Optical SWIPT, as known as simultaneous light information and power transfer (SLIPT), has the potential for providing high-capacity communication and high-power wireless charging. However, SLIPT technologies based on light-emitting diodes have low efficiency due to energy dissipation over the air. Laser-based SLIPT technologies need strict positioning accuracy and scanning resolution, which may lead to the increase of costs and complexity. In this paper, we propose a mobile SLIPT scheme based on spatially separated laser resonator (SSLR) and intra-cavity second harmonic generation. The power and data are transferred via separated frequencies, while they share the same self-aligned resonant beam path, without the needs of receiver positioning and beam steering. We establish the analysis model of the resonant beam power and its second harmonic power. Numerical results show that the proposed system can achieve watt-level battery charging power and above 10-bit/s/Hz achievable rate at 6-m distance, which satisfies the requirements of most indoor mobile devices. [ABSTRACT FROM AUTHOR]

In this paper, we propose a precoded faster-than-Nyquist (FTN) signaling technique for time-domain single-carrier index-modulated symbol transmission. More precisely, eigenvalue decomposition (EVD) precoding is adopted for the FTN transmission of data bits modulated by single-carrier time-domain index modulation (IM). While the FTN scheme increases the spectral efficiency and data rate by increasing the density of transmit symbols, the time-domain IM works towards the same objective while maintaining symbol sparsity. We analytically derive the constrained capacity of the proposed system. Our simulation results show that the proposed scheme has better bit error ratio (BER) performance than the conventional FTN-IM scheme, particularly for the scenario of a higher packing ratio. With the proposed scheme, a 2.5 dB performance gain is observed at the BER of 10−4, where the packing ratio is 0.7 and the roll-off factor is 0.5 in the channel-uncoded scenario. We further analyze our scheme’s performance by characterizing its minimum Euclidean distance and inter-symbol interference. Furthermore, we present a three-stage serially concatenated iterative detection architecture for the proposed EVD-FTN-IM signaling scheme. It is demonstrated in our simulations that a near-capacity BER performance is achievable in the proposed turbo-coded FTN-IM scheme. [ABSTRACT FROM AUTHOR]

Orthogonal Time Frequency Space (OTFS) modulation is a recently proposed scheme for time-varying narrowband channels in terrestrial radio-frequency communications. Underwater acoustic (UWA) and ultra-wideband (UWB) communication systems, on the other hand, confront wideband time-varying channels. Unlike narrowband channels, for which time contractions or dilations due to Doppler effect can be approximated by frequency-shifts, the Doppler effect in wideband channels results in frequency-dependent non-uniform shift of signal frequencies across the band. In this paper, we develop an OTFS-like modulation scheme – Orthogonal Delay Scale Space (ODSS) modulation – for handling wideband time-varying channels. We derive the ODSS transmission and reception schemes from first principles. In the process, we introduce the notion of $\omega$ -convolution in the delay-scale space that parallels the twisted convolution used in the time-frequency space. The preprocessing 2D transformation from the Fourier-Mellin domain to the delay-scale space in ODSS, which plays the role of inverse symplectic Fourier transform (ISFFT) in OTFS, improves the bit error rate performance compared to OTFS and Orthogonal Frequency Division Multiplexing (OFDM) in wideband time-varying channels. Furthermore, since the channel matrix is rendered near-diagonal, ODSS retains the advantage of OFDM in terms of its low-complexity receiver structure. [ABSTRACT FROM AUTHOR]

Due to the noisy indoor radio propagation channel, radio frequency (RF)-based location determination systems usually require a tedious calibration phase to construct an RF fingerprint of the area of interest. This fingerprint varies with the used mobile device, changes of the transmit power of smart access points (APs), and dynamic changes in the environment; requiring re-calibration of the area of interest; which reduces the technology ease of use. In this paper, we present IncVoronoi: a novel system that can provide low-overhead accurate RF-based indoor localization that works in realistic environments. The basic idea is that the relative relation between the received signal strength from two APs at a certain location reflects the relative distance from this location to the respective APs. Building on this, IncVoronoi incrementally reduces the user ambiguity region based on refining the Voronoi tessellation of the area of interest. IncVoronoi also includes a number of modules to efficiently run in realtime as well as to handle practical deployment issues including the noisy wireless environment, obstacles in the environment, heterogeneous devices hardware, and smart APs. We analyze the complexity of IncVoronoi and further deploy it on different Android phones using the iBeacons and WiFi technologies in a university campus and a commercial building. Evaluation of IncVoronoi with a side-by-side comparison with traditional fingerprinting techniques shows that it can achieve a consistent median accuracy less than 1.9m under different scenarios with a low beacon density of one beacon every 22m $^2$ 2 . Compared to fingerprinting techniques, whose accuracy degrades by at least 156 percent, this accuracy comes with no training overhead and is robust to the different user devices, different transmit powers, and over temporal changes in the environment. This highlights the promise of IncVoronoi as a next generation indoor localization system. [ABSTRACT FROM AUTHOR]

Terrestrial broadcast has traditionally targeted TV receivers in the home. But today’s most popular screens are those of SmartPhones and Tablet PCs. (Painful) Experience has shown that in order to reach those gadgets, IEEE- and 3GPP-specified solutions are required. Starting with TOoL+, the authors have proposed bridges between traditional broadcast and today’s wireless connectivity. Within the set of specifications of 3GPP such bridges named MBS, MBMS, and FeMBMS now exist – with limited acceptance by cellular network operators so far. The rapidly growing number of popular data services to SmartPhones, connected cars, etc., and 5G New Radio may change this in the future. Therefore, this paper presents a broadcast extension of today’s 5G New Radio supporting the implementation of High Tower High Power/Medium Power Medium Tower networks overlaying cellular networks. The extension was implemented using software defined radio and tested in a real-world field trial in Germany. [ABSTRACT FROM AUTHOR]

Pedestrian Dead Reckoning (PDR) is a good alternative positioning method in Global Navigation Satellite Systems (GNSS)-challenged environments. It has the advantage in terms of infrastructure-independent, while the disadvantage is that, the estimated errors grow rapidly with time. The Digital Terrestrial Multimedia Broadcasting (DTMB) signals have strong transmission power, which contributes to better urban propagation and building penetration than GNSS signals. So, in this paper, an enhanced PDR algorithm aided with DTMB signals is proposed. In the study, a complete software-defined radio receiver is developed to estimate the Doppler speed and range information from DTMB signals. To reduce the accumulated errors of the PDR, the Extended Kalman Filter (EKF) algorithm is carried out to fuse the information of Doppler speed and ranging from the DTMB signals, as well as the information of walking speed and heading from the PDR. The results of the field tests showed that the 95% positioning error of the proposed algorithm is less than 3.94 m, while the PDR only is less than 9.19 m, which suggests the effectiveness of the proposed method to provide continuous positioning by fusing DTMB signals with PDR. [ABSTRACT FROM AUTHOR]

The joint transmission scheme of polar codes and sparse code multiple access (SCMA) has been regarded as a promising technology for future wireless communication systems. However, most of the existing polar-coded SCMA (PC-SCMA) systems suffer from high latency caused by the feedback iteration and list decoding. In addition, the error performance of PC-SCMA systems is unsatisfactory for ultra-reliable transmission. Inspired by the compelling benefits of non-binary polar codes, in this paper, we design a non-binary polar-coded SCMA (NB-PC-SCMA) system with a free order matching strategy to address the issues of delay and reliability. Specifically, we first formulate a joint factor graph for NB-PC-SCMA and propose a non-binary successive cancellation list (NB-SCL) and damping based joint iterative detection and decoding (NSD-JIDD) multiuser receiver to improve the BER and latency performance. Then, a lazy-search based NB-SCL (L-NB-SCL) decoding is proposed to reduce the computational complexity by simplifying the path search pattern of the list decoder. After that, we modify the update of user nodes for SCMA detection to improve the convergence error and finally propose the improved NSD-JIDD (ISD-JIDD) algorithm, which can avoid redundant operations by exploiting L-NB-SCL decoding. Simulation results show that the proposed NB-PC-SCMA system achieves better bit error rate (BER) performance and considerable latency gain when compared to its counterparts. In particular, the proposed ISD-JIDD can achieve similar BER performance of NSD-JIDD with less complexity. [ABSTRACT FROM AUTHOR]

Terahertz (THz) band communications are envisioned as a key technology for 6G and Beyond. As a fundamental wireless infrastructure, THz communication can boost abundant promising applications. In 2014, our team published two comprehensive roadmaps for the development and progress of THz communication networks, which helped the research community to start research on this subject afterwards. The topic of THz communications became very important and appealing to the research community due to 6G wireless systems design and development in recent years. Many papers are getting published covering different aspects of wireless systems using the THz band. With this paper, our aim is looking back to the last decade and revisiting the old problems and pointing out what has been achieved in the research community so far. Furthermore, in this paper, open challenges and new research directions still to be investigated for the THz band communication systems are presented, by covering diverse topics ranging from devices, channel behavior, communication and networking, to physical testbeds and demonstration systems. The key aspects presented in this paper will enable THz communications as a pillar of 6G and Beyond wireless systems in the next decade. [ABSTRACT FROM AUTHOR]

This paper proposes a modular on-road wireless power transfer system with interoperable power adjustment mechanism. The paper is anticipated to enhance the capability of on-road charging during the movement of automated guided vehicles (AGV), by which the traveling mileage is increased, while the battery volume is decreased. The system design includes an interoperable power adjustment technique based on the detected impedance, and the moving position of AGV can be, hence, comprehended so as to facilitate the adjustment of the output power from each transmission module in a more flexible way. Through the investigation of on-road charging efficiency, all of coil magnetic analysis, misalignment charging evaluation, system stress simulation, and resonant characteristics investigation are performed. Experimental results gained from software simulation and hardware realization are beneficial for AGV charging applications. [ABSTRACT FROM AUTHOR]

Non-stationary channel models play a crucial role in today’s communication systems. Mobile-to-mobile channels are known to exhibit non-stationary behavior caused by the movement of transmitter and receiver. Non-stationarity can be addressed by introducing time-variant stochastic functions such as the time-variant instantaneous Doppler probability density function or time-variant instantaneous characteristic function. An algebraic analysis of the time-variant Doppler probability density function (pdf) in a classical Cartesian coordinate system is only numerically tractable due to trigonometric functions in the resulting expressions. In contrast, it has been shown that by using prolate spheroidal coordinates for 2D vehicle-to-vehicle channels the algebraic analysis becomes analytically tractable. In this paper, the analysis is extended to air-to-air channels. It is shown that the time-variant Doppler pdf can be represented without trigonometric functions. The description of the Doppler frequency in prolate spheroidal coordinates allows describing it as an algebraic curve. This permits the use of algebraic methods to analyze the Doppler frequency and derive the boundaries of the resulting Doppler pdf. Using the developed tools, we have investigated exemplary air-to-air scenarios. However, the methodology can be extended to any air-to-air configuration. [ABSTRACT FROM AUTHOR]

In coded caching, a single server is connected to a set of users through a shared bottleneck link, which is assumed to be error free. During non-peak hours, all the users fill their local cache with portions of the files available. During the delivery phase, each user requests a file and the server delivers coded transmissions to meet the demands. In this paper, the links between the server and the users are assumed to be error prone. Prefetching errors are also considered. A new delivery scheme is required to meet the demands of each user even after receiving a finite number of transmissions in error in the presence of erroneous portions of files in the cache. The minimum average rate and minimum peak rate for this problem are characterized. Closed form expressions for average and peak rates for a particular caching scheme, namely, symmetric batch prefetching are established when there are no prefetching errors. An optimal linear error correcting delivery scheme is proposed for coded caching problems with symmetric batch prefetching in the absence of prefetching errors. In addition to this, lower bounds are established for the optimal rate required when there are prefetching errors in symmetric batch prefetching. [ABSTRACT FROM AUTHOR]

This paper derives upper and lower bounds on the secrecy capacity-memory tradeoff of a wiretap erasure broadcast channel (BC) with ${\mathsf{K}}_{w} $ weak receivers and ${\mathsf {K}}_{s} $ strong receivers, where weak receivers and strong receivers have the same erasure probabilities and cache sizes, respectively. The lower bounds are achieved by the schemes that meticulously combine joint cache-channel coding with wiretap coding and key-aided one-time pads. The presented upper bound holds more generally for arbitrary degraded BCs and arbitrary cache sizes. When only weak receivers have cache memories, upper and lower bounds coincide for small and large cache memories, thus providing the exact secrecy capacity-memory tradeoff for this setup. The derived bounds further allow us to conclude that the secrecy capacity is positive even when the eavesdropper is stronger than all the legitimate receivers with cache memories. Moreover, they show that the secrecy capacity-memory tradeoff can be significantly smaller than its non-secure counterpart, but it grows much faster when cache memories are small. This paper also presents a lower bound on the global secrecy capacity-memory tradeoff where one is allowed to optimize the cache assignment subject to a total cache budget. It is close to the best known lower bound without secrecy constraint. For small total cache budget, the global secrecy capacity-memory tradeoff is achieved by assigning all the available cache memory uniformly over all the receivers if the eavesdropper is stronger than all the legitimate receivers, and it is achieved by assigning the cache memory uniformly only over the weak receivers if the eavesdropper is weaker than the strong receivers. [ABSTRACT FROM AUTHOR]

This paper provides a comprehensive review of the emerging research area of mobile molecular communication. In mobile molecular communication, sender and receiver bionanomachines as well as associated nodes in the environment exhibit dynamic behavior in the sense that they are mobile and communicate while they move. This paper presents a model of mobile bionanomachines and uses the model to discuss how groups of such bionanomachines working in unison can provide useful functionalities. This paper illustrates several functionalities by applying mobile molecular communication to the concept of cooperative drug delivery. Unsolved research challenges in this area are outlined and discussed. [ABSTRACT FROM AUTHOR]

We present an algorithm that efficiently performs blind decoding of MIMO signals. That is, given no channel state information (CSI) at either the transmitter or the receiver, our algorithm takes a block of samples and returns an estimate of the underlying data symbols. In prior work, the problem of blind decoding was formulated as a non-convex optimization problem. In this paper, we present an algorithm that efficiently solves this non-convex problem in practical settings. This algorithm leverages the concepts of linear and mixed-integer linear programming. Empirically, we show that our technique has an error performance close to that of zero-forcing with perfect CSI at the receiver. Initial estimates of the run time of the algorithm presented in this paper suggest that the real-time blind decoding of MIMO signals is possible for even modest-sized MIMO systems. [ABSTRACT FROM AUTHOR]

This paper considers the problem of channel coding over Gaussian intersymbol interference (ISI) channels with a given decoding rule. Specifically, it is assumed that the mismatched decoder has an incorrect assumption on the channel impulse response. The mismatch capacity is the highest achievable rate for a given decoding rule. The existing achievable rates for channels and decoding metrics with memory (as in our model) are currently available only in the form of multi-letter expressions that cannot be calculated. Consequently, they provide little insight on the mismatch problem. In this paper, we derive the computable formulas of achievable rates and discuss some implications of our results. Our achievable rates are based on two ensembles: the ensemble of codewords generated by an autoregressive process and the ensemble of codewords drawn uniformly over a “type class” of real-valued sequences. We provide a few numerical results of our achievable rates, as functions of the mismatched ISI parameters. Finally, we compare our results with universal decoders which are designed outside the true class of channels that we consider in this paper. [ABSTRACT FROM AUTHOR]

Broadcasting signals have been recognized as promising candidates for navigation and positioning needs. However, in most single frequency broadcasting networks, the transmitter confusion problem poses a huge obstacle. Not holding the transmitter identities, the receiver cannot determine the distance to the transmitters, let alone its own position. What’s worse, considering the existence of multipath propagation, the receiver is unable to distinguish line of sight (LOS) components from non line of sight components, which makes positioning even harder. In this paper, a two-step method is proposed to solve the positioning problem in single frequency networks (SFNs) under multipath propagation yet with direct path. First, a probability approach is proposed to identify all LOS components iteratively. Then, it is proved in this paper that a receiver can determine its position when receiving LOS signals from at least five transmitters without the knowledge of transmitter identities. Detailed analysis is carried out in this paper to derive error bounds and performance limits from different perspectives. Simulation results show that the proposed algorithm can achieve high accuracy of positioning across multiple environments. Besides, the proposed methodology is general, which can be used in any SFN or other wireless networks for positioning needs. [ABSTRACT FROM AUTHOR]

This paper derives a maximum-likelihood decision rule to detect the signaling information conveyed by the bootstrap for an ATSC 3.0 system and proposes an iterative detection scheme to improve the detection performance. The proposed detection scheme iteratively averages the channel estimates for two consecutive bootstrap symbols by exploiting the previously detected symbol. The simulation results show that the proposed detection scheme can obtain a signal-to-noise ratio gain of approximately 2.0 dB at a frame error rate of $10^{-3}$ compared to the conventional detection scheme. Furthermore, this paper analyzes the computational complexity of the proposed detection scheme and presents the number of iterations sufficient to provide a good performance-complexity trade-off. [ABSTRACT FROM AUTHOR]

This paper considers a network where a node wishes to transmit a source message to a legitimate receiver in the presence of an eavesdropper. The transmitter secures its transmissions employing a sparse implementation of random linear network coding (RLNC). A tight approximation to the probability of the eavesdropper recovering the source message is provided. The proposed approximation applies to both the cases where transmissions occur without feedback, or where the reliability of the feedback channel is impaired by an eavesdropper jamming the feedback channel. An optimization framework for minimizing the intercept probability by optimizing the sparsity of the RLNC is also presented. Results validate the proposed approximation and quantify the gain provided by our optimization over solutions where non-sparse RLNC is used. [ABSTRACT FROM AUTHOR]

This paper develops novel deep learning-based architectures and design methodologies for an orthogonal frequency division multiplexing (OFDM) receiver under the constraint of one-bit complex quantization. Single bit quantization reduces greatly the complexity and power consumption but makes accurate channel estimation and data detection difficult. This is particularly true for multicarrier waveforms that have high peak-to-average power ratio in the time domain and fragile subcarrier orthogonality in the frequency domain. The severe distortion for one-bit quantization typically results in an error floor even at moderately low signal-to-noise-ratio (SNR) such as 5 dB. For channel estimation (using pilots), we design a novel generative supervised deep neural network that can be trained with a reasonable number of pilots. After channel estimation, a neural network-based receiver—specifically, an autoencoder—jointly learns a precoder and decoder for data symbol detection. Since quantization prevents end-to-end training, we propose a two-step sequential training policy for this model. With synthetic data, our deep learning-based channel estimation can outperform least squares channel estimation for unquantized (full-resolution) OFDM at average SNRs up to 14 dB. For data detection, our proposed design achieves lower bit error rate (BER) in fading than unquantized OFDM at average SNRs up to 10 dB. [ABSTRACT FROM AUTHOR]

Motivated by the idea of “transmitting energy and information simultaneously,” we investigate, in this paper, the impact of constraints on the amount of energy that individual symbols carry, i.e., minimum amplitude constraints. We consider a Gaussian mixture noise channel with both minimum and peak amplitude constraints. First, we prove that the capacity-achieving input has a discrete distribution with a finite number of probability mass points. Then, we further investigate the number and positions of the probability mass points for the capacity-achieving input. Specifically, when the interference is constant and known at both the transmitter and the receiver, it can be totally eliminated so that the channel operates like an AWGN channel. In this case, we give a theorem to determine whether the optimal input is binary. For more general cases, such as non-binary inputs and non-constant interference, we investigate optimal inputs and capacities via numerical computations. [ABSTRACT FROM AUTHOR]

In the $q$ -ary online (or “causal”) channel coding model, a sender wishes to communicate a message to a receiver by transmitting a codeword $\mathbf {x} =(x_{1},\ldots,x_{n}) \in \{0,1,\ldots,q-1\}^{n}$ symbol-by-symbol via a channel limited to at most $pn$ errors and $p^{*} n$ erasures. The channel is “online” in the sense that at the $i$ th step of communication the channel decides whether to corrupt the $i$ th symbol or not based on its view so far, i.e., its decision depends only on the transmitted symbols $(x_{1},\ldots,x_{i})$. This is in contrast to the classical adversarial channel in which the corruption is chosen by a channel that has full knowledge of the sent codeword $\mathbf {x}$. In this paper, we study the capacity of $q$ -ary online channels for a combined corruption model, in which the channel may impose at most $pn$ errors and at most $p^{*} n$ erasures on the transmitted codeword. The online channel (in both the error and erasure case) has seen a number of recent studies, which present both upper and lower bounds on its capacity. In this paper, we give a full characterization of the capacity as a function of $q,p$ , and $p^{*}$. [ABSTRACT FROM AUTHOR]

Prolific growth of miniaturized devices has led to widespread use of wearable devices and physiological sensors. The state-of-art technique for connecting these devices and sensors is through wireless radio waves. However, wireless body area wireless body area network (WBAN) suffers from limited security (wireless signals from energy-constrained sensors can be snooped by nearby attackers), poor energy-efficiency (up conversion and down conversion), and self-interference. Human body communication (HBC), which uses human body as a conducting medium, has emerged as a new alternative physical layer for WBAN, as it can enable communication with better energy efficiency and enhanced security. Broadband (BB) HBC uses the human body channel as a broadband communication medium and can enable higher energy efficiency compared to narrowband HBC. However, due to the antenna effect of human body, ambient interferences get picked up from the environment, proving to be one of the primary bottlenecks for BB-HBC systems. In this paper, we analyze the performance of an integrating dual data rate (I-DDR) receiver, which enables interference robust BB-HBC, under continuous wave (CW), amplitude modulated (AM), and frequency modulated (FM) interferences. Theoretical derivations along with simulations provide key insights into the behavior of I-DDR receiver under different interference scenarios, highlighting the efficacy (>22 dB improvement in SIR tolerance for both FM and AM) of the technique. Finally, measurements are carried out by applying the I-DDR principle on signals transmitted through the human body and captured on an oscilloscope. Measurements from an I-DDR receiver fabricated in TSMC 65 nm technology shows <10−4 BER in presence of CW, AM, and FM interference with −21 dB SIR further demonstrating the efficacy of the I-DDR method in interference rejection. [ABSTRACT FROM AUTHOR]

Sending broadcast messages is an efficient means of communicating in emergency situations, especially during serious disasters. This paper focuses on the digital audio broadcast (DAB) system. First, several new techniques are reported to enhance the emergency warning message (EWM) receiving and display functionalities for both personal and public DAB terminals. Then, a novel bidirectional communication method between two DAB transmitters is proposed, to enable the communication to and from the disaster area and the outside. Experiments show that the EWM can be correctly sent to the intended DAB terminals within 0.2–3 s, and the existing public light emitting diode screens can be expanded as DAB EWM terminals without affecting their normal functions. The bidirectional multimedia communication between two DAB transmitters is also successfully demonstrated. The proposed techniques expand upon the DAB’s existing functionality, and can benefit more people during emergencies. [ABSTRACT FROM AUTHOR]

In this paper, a robotic arm moving along a user-defined trajectory is used to calibrate a short-range magnetic positioning system (MPS). Such system estimates the position and attitude of an active transmitting coil by measuring the induced voltage on a set of fixed receiving coils, with known position and orientation. This estimate is obtained by solving an optimization problem that can be decomposed into a linear and a reduced nonlinear problem. Then, a Kalman Filter is used to process the estimated positions and obtain smooth trajectories. Data acquisition and processing are performed in real time by the MPS. In this context, the robotic arm is used to provide ground truth, i.e., to move the active coil along a known trajectory, while simultaneously the MPS estimates the position of the active coil. Such ground-truth information is then used to calibrate the MPS and improve its accuracy. To align the robotic arm with the MPS, a preliminary calibration procedure of the robot is performed. Then, a wide ground-truth trajectory is used to estimate the calibration parameters of the MPS itself, namely, the positions and orientation of the fixed coils. To validate the efficiency of the calibration procedure, the accuracy of the MPS is evaluated across several trajectories. The results show that the mean positioning error is less than 3 mm. Finally, an on-the-fly calibration method simultaneously estimating positions and attitudes of both the active coil and all the receivers is investigated. [ABSTRACT FROM AUTHOR]

This paper proposes a broadcast strategy for the single-user slowly fading channel in which the transmission power is supplied by an energy harvesting unit. In this strategy, the channel state information (CSI) is known only to the receiver, and the transmitter is assumed to be oblivious to the CSI. The broadcast approach enables preventing outage events in the face of the lack of CSI at the transmitter. In the proposed broadcast approach, the transmitter splits its message into multiple superimposed information layers. This facilitates sustaining reliably decodable transmission rates adapted to the unknown state of the randomly-varying fading state of the channel. The objective is to characterize the optimal allocation of the randomly varying harvested power over time and across information layers in the contexts of maximizing the average communication rate and minimizing the likelihood of outage. First, the setting in which the transmitter has non-causal and complete information about the state of the energy harvesting process is considered. A closed-form characterization of the optimal allocation of power across layers is established, and an algorithm that analytically determines the exact optimal allocation of power over time is provided. Furthermore, an online algorithm is proposed for a setting in which the energy harvesting process is known only causally to the transmitter. [ABSTRACT FROM AUTHOR]

We present an ultralow-power millimeter-sized ultrasonic wake-up receiver (WuRx) that uses precharged ultrasonic transducers to wirelessly receive wake-up signatures. Our WuRx takes advantage of the low carrier frequency afforded by the low speed of sound to achieve high impedance, and thus high sensitivity, operation in a millimeter-sized form factor. We discuss the system-level considerations that arise from the use of ultrasound as a mode of signature transmission, including the choice of operating frequency and the effect of transducer miniaturization on WuRx sensitivity. We describe the design of the receiver electronics and support our case for ultrasonic wake-up with thorough wireless measurements of error rate and electrical characterization of multiple dice from the same wafer lot. The receiver electronics are fabricated in 65-nm CMOS technology, while the receiver transducer is fabricated by means of a custom in-house process. The receiver achieves a sensitivity of −59.7 dBm at a bit error rate (BER) of 10−3 with a power consumption of 8 nW and a footprint of 14.5 mm2. Our benchmarking shows that the proposed WuRx achieves the lowest system area/aperture of all RF and acoustic WuRxs in the literature (1.45 $\times $ smaller than the state of the art) while maintaining competitive sensitivity and power consumption. [ABSTRACT FROM AUTHOR]

This paper presents a multi-standard fully connected hybrid beamforming (FC-HBF) receiver that can be reconfigured between two fully connected two-stream multi-input-multi-output (MIMO) modes at 28- or 37-GHz band, and an inter-band carrier-aggregation (CA) mode enabling concurrent single-stream operation at 28 and 37 GHz. A new image-reject (IR) heterodyne beamforming architecture is introduced that facilitates easy reconfiguration. Concurrent dual-band operation of the beamformer front end is achieved by using an inherently wideband Cartesian-combining-based RF-domain complex-weighting architecture, which is implemented using coupled-resonator-based dual-band gain stages, and current-mode dual-band active combiners. The downconversion stage comprises a cascade of complex-quadrature mixing stages that combines Cartesian complex-weighting operation with image rejection. A new quadrature error detection and calibration scheme is also introduced to improve the image rejection of the proposed architecture. A minimum mean-square error (MMSE) beam adaptation technique, introduced for the first time in an RF or hybrid beamformer, breaks the need for individual access to the beamformer inputs needed in a traditional least-mean-square (LMS) scheme and allows both main lobe and null adaptation. A 28-/37-GHz hybrid beamforming receiver with four antenna inputs and two baseband output streams is designed in 65-nm CMOS that demonstrates the above features. In each antenna path, the receiver achieves 33-dB (26.5 dB) peak conversion gain, 2.75-GHz (3.75 GHz) RF bandwidth, and 5.7-dB (8.5 dB) NF at 28 GHz (37 GHz). The entire receiver consumes 310 mW and occupies 2.2 mm2 core area. Extensive characterization results for single-element and several multi-element scenarios are presented including concurrent dual-band receiving (>35-dB image rejection), null-steering (>25-dB peak to null for two elements), and multi-element CA (~50-dB inter-carrier interference rejection). [ABSTRACT FROM AUTHOR]

This paper considers a low-complexity iterative linear minimum mean square error (LMMSE) multiuser detector for the multiple-input and multiple-output system with nonorthogonal multiple access (MIMO-NOMA), where multiple single-antenna users simultaneously communicate with a multiple-antenna base station (BS). While LMMSE being a linear detector has a low complexity, it has suboptimal performance in multiuser detection scenario due to the mismatch between LMMSE detection and multiuser decoding. Therefore, in this paper, we provide the matching conditions between the detector and decoders for MIMO-NOMA, which are then used to derive the achievable rate of the iterative detection. We prove that a matched iterative LMMSE detector can achieve the optimal capacity of symmetric MIMO-NOMA with any number of users, the optimal sum capacity of asymmetric MIMO-NOMA with any number of users, all the maximal extreme points in the capacity region of asymmetric MIMO-NOMA with any number of users, and all points in the capacity region of two-user and three-user asymmetric MIMO-NOMA systems. In addition, a kind of practical low-complexity error-correcting multiuser code, called irregular repeat-accumulate code, is designed to match the LMMSE detector. Numerical results shows that the bit error rate performance of the proposed iterative LMMSE detection outperforms the state-of-art methods and is within 0.8 dB from the associated capacity limit. [ABSTRACT FROM AUTHOR]

A novel localization algorithm, which considers nonline-of-sight (NLOS) propagation, is proposed in this paper. By introducing a transfer function that relates the field at a given receiver to the source as a function of frequency and position, the NLOS effect can be mitigated and the propagation channel can be calibrated back to free space. The simulation results demonstrate that the proposed algorithm performs much better than that using the usual line-of-sight time difference of arrival (TDOA) localization, and the accuracy is only limited by the sampling frequency. The measurements verify the improvement in using the improved TDOA method versus the usual TDOA method. [ABSTRACT FROM AUTHOR]

Downlink transmission into frequency-selective links experiencing different coherence bandwidths and coherence times has obvious practical relevance, but is often addressed via assuming for all users the coherence conditions corresponding to the fastest, most dispersive user. This paper demonstrates an alternative approach that directly exploits the differences between coherence bandwidth and coherence time of users under frequency-selective conditions, showing that it can lead to significant new efficiencies and gains. More specifically, we study a two-user downlink frequency-selective channel under three broad conditions of disparity between the link qualities: when the disparity is in coherence time, in coherence bandwidth, and in both coherence time and coherence bandwidth. Each of the coherence scenarios calls for a distinct treatment; for each, we provide an analysis demonstrating the gains in achievable rates due to exploiting coherence disparity. Numerical simulations demonstrate the advantages of the proposed schemes. [ABSTRACT FROM AUTHOR]

Over the past decade, the bulk of wireless traffic has shifted from speech to content. This shift creates the opportunity to cache part of the content in memories closer to the end users, for example in base stations. Most previous paper focuses on the reduction of load in the backhaul and core networks due to caching, i.e., on the benefits caching offers for the wireline communication link between the origin servers and the caches. In this paper, we are instead interested in the benefits caching can offer for the wireless communication link between the caches and the end users. To quantify the gains of caching for this wireless link, we consider an interference channel in which each transmitter is equipped with an isolated cache memory. Communication takes place in two phases, a content placement phase followed by a content delivery phase. The objective is to design both the placement and the delivery phases to maximize the rate in the delivery phase in response to any possible user demands. Focusing on the three-user case, we show that through careful joint design of these phases, we can reap three distinct benefits from caching: a load balancing gain, an interference cancellation gain, and an interference alignment gain. In our proposed scheme, load balancing is achieved through a specific file splitting and placement, producing a particular pattern of content overlap at the caches. This overlap allows to implement interference cancellation. Furthermore, it allows us to create several virtual transmitters, each transmitting a part of the requested content, which increases interference-alignment possibilities. [ABSTRACT FROM AUTHOR]

This paper presents an energy-/area-efficient digitally controlled oscillator (DCO)-based phase-tracking Receiver for Internet-of-Things (IoT) applications. The RX leverages the constant-envelope nature of frequency shift keying modulation adopted in many IoT protocols, e.g., IEEE802.15.4 and Bluetooth low energy (BLE), to enhance the energy efficiency and to reduce the chip area. The proposed RX, with the DCO acting as a local oscillator (LO) and binary frequency feedback, promotes low-power and low-voltage circuit design, while a data-aided carrier-frequency tracking ensures the received carrier stability without a power-/area-hungry phase-locked loop (PLL). The RX avoids a compromise between a power-hungry I/Q LO generation and the image rejection in traditional RXs. An equivalent mathematical model is further presented, which helps to analyze and optimize the frequency response of the proposed RX. Fabricated in 40-nm CMOS, the RX consumes 1.55 mW from a 0.85-V supply and has a −87-dBm sensitivity at 2 Mb/s, which leads to a 0.77-nJ/b energy efficiency and 178-dB RX sensitivity FoM. [ABSTRACT FROM AUTHOR]

This paper presents a four-level pulse amplitude modulation (PAM4) quarter-rate receiver that efficiently compensates for moderate channel loss in a robust manner through background adaptation of the receiver thresholds and equalization taps. The front-end utilizes an input single-stage continuous-time linear equalizer (CTLE) to boost the main cursor and relax the pre-cursor cancellation requirement, requiring only a 2-tap pre-cursor feed-forward equalizer (FFE) on the transmitter side. A 2-tap decision feedback equalizer (DFE) follows that includes one finite impulse response (FIR) tap and one infinite impulse response (IIR) tap to cancel first post-cursor and long-tail inter-symbol interference (ISI), respectively. In addition to the per-slice main three data samplers, a single error sampler is utilized for background threshold control and an edge-based sampler performs both phase-locked loop (PLL)-based clock and data recovery (CDR) phase detection and generates information for background DFE tap adaptation. Fabricated in general purpose (GP) 65-nm CMOS, the 56-Gb/s receiver achieves 4.63 mW/Gb/s and compensates for up to 20.8-dB loss at a bit error rate (BER) < 10−12 when operated with a 2-tap FFE transmitter. [ABSTRACT FROM AUTHOR]

This paper presents a focusing solution for high-resolution high forward-looking bistatic synthetic aperture radar with nonequal platform velocities (NPV-BFSAR). In NPV-BFSAR, due to the high-resolution SAR and high forward-looking angle, range cell migration, and two-dimensional spatial variation are more serious. To solve this problem, a modified imaging algorithm based on second-order keystone transform (KT) and modified nonlinear chirp scaling (NLCS) method are proposed. The second-order KT method can correct the linear range cell migration and reduce the strong coupling between azimuth and range. The proposed modified azimuth NLCS algorithm is more accurate than traditional NLCS algorithm on eliminating the variation of azimuth reference function that can improve the focus quality of edge targets. Finally, some simulation results confirm the efficiency of the proposed algorithm. [ABSTRACT FROM AUTHOR]

This paper proposes a low budget solution to detect and possibly track space debris and satellites in Low Earth Orbit. The concept consists of a space-borne radar installed on a cubeSat flying at low altitude and detecting the occultations of radio signals coming from existing satellites flying at higher altitudes. The paper investigates the feasibility and performance of such a passive bistatic radar system. Key performance metrics considered in this paper are: the minimum size of detectable objects, considering visibility and frequency constraints on existing radio sources, the receiver size, and the compatibility with current cubeSat's technology. Different illuminator types and receiver altitudes are considered under the assumption that all illuminators and receivers are on circular orbits. [ABSTRACT FROM AUTHOR]

Visible light communications (VLC) has been studied thoroughly in recent years as an alternative or complementary technology to radio frequency communications. The reliability of VLC channels highly depends on the availability and alignment of line of sight links. In this paper, we study the effect of random receiver orientation for mobile users over VLC downlink channels, which affects the existence and quality of line of sight links. Based on the statistics of the receiver location and relative orientation with respect to the transmitter LED, we develop an analytical framework to characterize the statistical distribution of VLC downlink channels, which is then utilized to obtain the outage probability and the bit error rate. Our analysis is generalized for arbitrary distributions of relative orientation and location for a single transmitter, and extended to multiple transmitter case for some certain scenarios. Extensive Monte Carlo simulations show a perfect match between the analytical and the simulation data in terms of both the statistical channel distribution and the resulting bit error rate. Our results also characterize the channel attenuation due to random receiver orientation and location for various scenarios of interest. [ABSTRACT FROM AUTHOR]

This paper analyzes how the distortion created by hardware impairments in a multiple-antenna base station affects the uplink spectral efficiency (SE), with a focus on massive multiple input multiple output (MIMO). This distortion is correlated across the antennas but has been often approximated as uncorrelated to facilitate (tractable) SE analysis. To determine when this approximation is accurate, basic properties of distortion correlation are first uncovered. Then, we separately analyze the distortion correlation caused by third-order non-linearities and by quantization. Finally, we study the SE numerically and show that the distortion correlation can be safely neglected in massive MIMO when there are sufficiently many users. Under independent identically distributed Rayleigh fading and equal signal-to-noise ratios (SNRs), this occurs for more than five transmitting users. Other channel models and SNR variations have only minor impact on the accuracy. We also demonstrate the importance of taking the distortion characteristics into account in the receive combining. [ABSTRACT FROM AUTHOR]

Chemical reactions are a prominent feature of molecular communication systems, with no direct parallels in wireless communications. While chemical reactions may be used inside the transmitter nodes, receiver nodes, or the communication medium, we focus on its utility in the medium in this paper. Such chemical reactions can be used to perform computation over the medium as molecules diffuse and react with each other (physical-layer computation). We propose the use of chemical reactions for the following purposes: 1) to reduce signal-dependent observation noise of receivers by reducing the signal density; 2) to realize molecular physical-layer network coding (PNC) by performing the natural XOR operation inside the medium; and 3) to reduce the inter-symbol interference (ISI) of other transmitters by canceling out the remaining molecules from previous transmissions. To make the ideas formal, we consider an explicit two-way relaying example with a transparent receiver (which has a signal-dependent noise). The proposed ideas are used to define a modulation scheme (which we call the PNC scheme). We compare the PNC with a previously proposed scheme for this problem, where the XOR operation is performed at the relay node (using a molecular logic gate). We call the latter, the straightforward network coding (SNC). It is observed that in addition to the simplicity of the proposed PNC scheme, it outperforms the SNC scheme especially when we consider ISI. [ABSTRACT FROM AUTHOR]

A four-path filter/mixer for surface acoustic wave (SAW)-less frequency division duplex (FDD) radio receivers is proposed, targeting high linearity and compression requirements. A bottom-plate mixing technique improves linearity by reducing the gate-source voltage modulation of the MOSFET switches. Differential bottom-plate mixing allows for switch sharing which halves the effective switch resistance to reduce drain-source voltage modulation. The first four-path switch-RC filter stage with bottom-plate mixing and a shared switch renders 2nd-order voltage-domain RF-bandpass filtering around the LO frequency. Extra out-of-band rejection is implemented combined with $V$ – $I$ conversion and zero-IF frequency down-conversion in the second cross-coupled switch-RC four-path stage, which offers a low-ohmic high-linearity current path for out-of-band interferers. A prototype chip fabricated in a 28-nm CMOS technology achieves an out-of-band IIP3 of +44 dBm, IIP2 of +90 dBm and blocker 1-dB gain-compression point of +13 dBm for a blocker frequency offset of 80 MHz. At this offset frequency, the measured desensitization is only 0.6 dB for a 0-dBm blocker, and 3.5 dB for a 10-dBm blocker at 0.7-GHz LO (i.e., 6- and 9-dB blocker noise figure). The chip consumes 38–96 mW for LO-frequencies of 0.1–2 GHz and occupies an active area of 0.49 mm2. [ABSTRACT FROM AUTHOR]

The goal of this paper is to localize a resident in indoor environments by using motion information from distributed environmental sensors and body activity information from wearable sensors. The passive infrared sensor nodes distributed in a home provide binary information about human motion in their field of views, while the wearable inertial measurement unit sensor node collects motion data that can be used in body activity recognition, walking velocity, and heading estimation. Basic human activities such as sitting, sleeping, standing, and walking are recognized. We proposed a particle filter-based sensor fusion algorithm that takes advantage of the human location/activity correlation in indoor environments to increase the localization accuracy. Experiments were conducted in a mock apartment testbed. We used the ground truth data obtained from a motion capture system to evaluate the results. Note to Practitioners—This paper is motivated by a goal to realize various home automation applications through human localization. For example, with the knowledge of human location, lighting, and air conditioning systems can be more efficiently managed, or a home service robot can provide better service to the resident. There currently lacks an accurate human localization method in indoor environments. The theoretical framework proposed in this paper aims to combine simple environmental sensors (passive infrared sensors) and a single wearable motion sensor to accurately track human locations. This method reduces the intrusiveness to the human, while keeping the cost of the infrastructure low. The theoretical framework has been tested and evaluated in a mock apartment environment as a proof of concept. For deployment into real homes, we need to conduct more realistic tests and thorough evaluation of the system. It is also necessary to reduce the size and weight of the wearable motion sensor and simplify the installation of the environmental sensors. [ABSTRACT FROM AUTHOR]

In this paper, we propose a method to reuse the cyclic-prefix (CP) intervals of an ongoing OFDM link, by another link, without degrading the OFDM link performance. We label the link that reuses the CP-intervals as CPLink, as they use only the CP-intervals of the ongoing link labeled, MainLink. We leverage the fact that the most commonly used OFDM receivers discard the samples in CP-intervals to design the CPLink that ensures below-noise-floor interference at every MainLink-receiver. The key contribution in this paper is the design and study of zero-knowledge CPLink, in which the CPLink-transmitter ensures below-noise-floor interference at every MainLink-receiver with no knowledge about the locations or the number of MainLink-receivers. We analytically show that the zero-knowledge CPLink capacity is positive. For LTE frame structure with 20-MHz bandwidth and 2-km cell-radius, we evaluate the CPLink for two kinds of CPLink-receivers: full-duplex base-station and a half-duplex device. Even for the cell-edge CPLink-transmitters, full-duplex zero-knowledge CPLink data rates can be up to 20 Mbps (60 Mbps) when the CP duration is ~7% (25%) of the data-symbol duration. The half-duplex CPLink rate is 5–40 Mbps when the CPLink-transmitter is within 250 m of CPLink-receiver. CPLink capacity is found to increase near-linearly with the CP duration, thus mitigating CP overhead. [ABSTRACT FROM AUTHOR]

In this paper, we consider diffusion-based molecular communication with and without drift between two static nano-machines. We employ type-based information encoding, releasing a single molecule per information bit. At the receiver, we consider an asynchronous detection algorithm which exploits the arrival order of the molecules. In such systems, transposition errors fundamentally undermine reliability and capacity. Thus, in this paper, we study the impact of transpositions on the system performance. Toward this, we present an analytical expression for the exact bit error probability (BEP) caused by transpositions and derive computationally tractable approximations of the BEP for diffusion-based channels with and without drift. Based on these results, we analyze the BEP when background is not negligible and derive the optimal bit interval that minimizes the BEP. Simulation results confirm the theoretical results and show the error and goodput performance for different parameters such as block size or noise generation rate. [ABSTRACT FROM AUTHOR]

Analog least mean square (ALMS) loop is a promising method to cancel self-interference (SI) in in-band full-duplex (IBFD) systems. In this paper, the steady state analyses of the residual SI powers in both analog and digital domains are firstly derived. The eigenvalue decomposition is then utilized to investigate the frequency domain characteristics of the ALMS loop. Our frequency domain analyses prove that the ALMS loop has an effect of amplifying the frequency components of the residual SI at the edges of the signal spectrum in the analog domain. However, the matched filter in the receiver chain will reduce this effect, resulting in a significant improvement of the interference suppression ratio (ISR). It means that the SI will be significantly suppressed in the digital domain before information data detection. This paper also derives the lower bounds of ISRs given by the ALMS loop in both analog and digital domains. These lower bounds are joint effects of the loop gain, tap delay, number of taps, and transmitted signal properties. The discovered relationship among these parameters allows the flexibility in choosing appropriate parameters when designing the IBFD systems under given constraints. [ABSTRACT FROM AUTHOR]

This paper investigates the symmetric degrees of freedom (DoF) of multiple-input multiple-output (MIMO) cellular networks with $G$ cells and $K$ users per cell, having $N$ antennas at each base station and $M$ antennas at each user. In particular, we investigate techniques for achievability that are based on either decomposition with asymptotic interference alignment or linear beamforming schemes and show that there are distinct regimes of $(G,K,M,N)$ , where one outperforms the other. We first note that both one-sided and two-sided decomposition with asymptotic interference alignment achieve the same DoF. We then establish specific antenna configurations under which the DoF achieved using decomposition-based schemes is optimal by deriving a set of outer bounds on the symmetric DoF. Using these results, we completely characterize the optimal DoF of any $G$ -cell network with single-antenna users. For linear beamforming schemes, we first focus on small networks and propose a structured approach to linear beamforming based on a notion called packing ratios. Packing ratio describes the interference footprint or shadow cast by a set of transmit beamformers and enables us to identify the underlying structures for aligning interference. Such a structured beamforming design can be shown to achieve the optimal spatially normalized DoF (sDoF) of two-cell two-user/cell network and the two-cell three-user/cell network. For larger networks, we develop an unstructured approach to linear interference alignment, where transmit beamformers are designed to satisfy conditions for interference alignment without explicitly identifying the underlying structures for interference alignment. The main numerical insight of this paper is that such an approach appears to be capable of achieving the optimal sDoF for MIMO cellular networks in regimes where linear beamforming dominates asymptotic decomposition, and a significant portion of sDoF elsewhere. Remarkably, polynomial identity test appears to play a key role in identifying the boundary of the achievable sDoF region in the former case. [ABSTRACT FROM AUTHOR]

The dominate spectrum sharing paradigm of today is interference avoidance, where a secondary network can use the spectrum only when such a use is not interfering with the primary network. However, with the advances of physical-layer technologies, the mindset of this paradigm is being challenged. This paper explores a new paradigm called “transparent coexistence” for spectrum sharing between primary and secondary nodes in a multihop network environment. Under this paradigm, the secondary network is allowed to use the same spectrum simultaneously with the primary network as long as their activities are “transparent” (or “invisible”) to the primary network. Such transparency is accomplished through a systematic interference cancelation (IC) by the secondary nodes without any impact on the primary network. Although such a paradigm has been studied in the information theory (IT) and communications (COMM) communities, it is not well understood in the wireless networking community, particularly for multihop networks. This paper offers an in-depth study of this paradigm in a multihop network environment and addresses issues such as scheduling (both in frequency channels and time slots) and IC (to/from primary network and within the secondary network). Through a rigorous modeling and formulation, problem formulation, solution development, and simulation results, we show that transparent coexistence paradigm offers significant improvement in terms of spectrum access and throughput performance as compared to the current prevailing interference avoidance paradigm. [ABSTRACT FROM AUTHOR]

Iterative decoding is an efficient error-correction tool based on the exchange of extrinsic probabilities between the constituent decoders. In this paper, the properties of the mutual information between the extrinsic LLR at the output of two constituent decoders are analyzed with application to turbo and LDPC codes. This is a bridge between information-theoretic analysis and practical implementations. It is proved here that the mutual information between extrinsics is a lower bound of the mutual information between each extrinsic and the transmitted message. In addition, an efficient online evaluation is provided in the paper with accuracy validated through numerical experiments. As an application, the mutual information between extrinsics is used for designing efficient stopping criterion and error detection rules at the decoder side. Two online methods for the estimation of optimal scaling factor to be applied to the extrinsic LLR are also derived. In contrast with most references, an analytical expression is obtained that does not require estimation of the actual transmitted bits. All results in the paper are derived for Gaussian distributed LLR with independent mean and variance. [ABSTRACT FROM PUBLISHER]

This paper analyzes the reliability and throughput of the telegram-splitting concept in the presence of inter-system and intra-system interference. Using telegram splitting, the data of one telegram is split into multiple sub-packets, which are then transmitted with temporal spacing. As a result, collisions with other telegrams destroy only some sub-packets that can be recovered using forward error correction. Consequently, the reliability of the data transmission in case of inter- and intra-system interference—a significant problem in license-exempt bands—is highly improved. In this paper, probabilities for the resulting telegram error rate of random media access systems using telegram splitting are derived. Furthermore, the achievable throughput is analyzed. The theoretical considerations in addition to simulation results prove the significant gain of the telegram-splitting concept for telemetry systems. [ABSTRACT FROM PUBLISHER]